Jerome L. Elkind

Reactive ion etching of HgCdTe with methane and hydrogen

Reactive ion etching (RIE) of HgCdTe using hydrogen and methane/hydrogen mixtures has been studied. The hydrogen RIE was found to form a Cd‐rich residue which resulted in a very rough surface and which gradually inhibited via formation. The addition of methane (∼25%) resulted in smoother etched surfaces and ultimately deeper vias without the residue. Aspect ratios (via depth to width) of ∼0.9 were attained using this RIE process. A very strong HgCdTe surface orientation dependence was noted regarding both etch rate and etched surface morphology. For short etch times, the [111B] surface etched faster than the [100] surface, which etched faster than the [111A] surface. On the other hand, the [111A] etched surface was far smoother than either the [111B] or [100] surfaces.

Detection of trinitrotoluene (TNT) extracted from soil using a surface plasmon resonance (SPR)-based sensor platform

An antibody-based competition assay has been developed using a surface plasmon resonance (SPR) sensor platform for the detection of trinitrotoluene (TNT) in soil extract solutions. The objective of this work is to develop a sensor-based assay technology to use in the field for real- time detection of land mines. This immunoassay combines very simple bio-film attachment procedures and a low-cost SPR sensor design to detect TNT in soil extracts. The active bio-surface is a coating of bovine serum albumin that has been decorated with trinitrobenzene groups. A blind study on extracts from a large soil matrix was recently performed and result from this study will be presented. Potential interferant studied included 2,4-dinitrophenol, 2,4- dinitrotoluene, ammonium nitrate, and 2,4- dichlorophenoxyacetic acid. Cross-reactivity with dinitrotoluene will be discussed. Also, plans to reach sensitivity levels of 1ppb TNT in soil will be described.

Fundamental system for biosensor characterization: application to surface plasmon resonance (SPR)

The aim of the described research is to develop a general system for characterizing and developing signal transduction systems for microbiosensors. The approach that we are using is applicable to signal transduction systems based on surface plasmon resonance, chemiluminescence, fluorescence, mass as well as other phenomena. The specific goal of our approach is to develop a general system that will allow for the systematic characterization of the effects of the affinity of the sensor specificity element for the target analyte, the effect of analyte mass on signal size and the general performance of the sensor system with respect to sensitivity and selectivity. At the same, time this system should allow for the characterization of the distribution of biospecificity elements on the sensor surface. We chose the anti-fluorescein monoclonal antibody approach for this development system, since the antigen fluorescein can be attached to many different molecules and organisms through free amine groups via reaction with fluorescein isothiocyanate. Also, well characterized monoclonal antibodies with a broad range of Kd values are available. We also describe rapid procedures for generating proteins for use in biosensor applications.

Detection of a polynitroaromatic compound using a novel polymer-based multiplate sensor

A novel sensor concept for detection of polynitroaromatic compounds has been developed in a partnership between Texas Instruments and the University of New Hampshire. The objective for this sensor is to demonstrate an explosive detection system designed specifically for field use. Our approach incorporates manufacturability and low cost while emphasizing field compatibility, usability, hand-held portability, selectivity, and sensitivity. The new device incorporates a novel multi-plate configuration and is based on colorimetric changes that occur when polynitroaromatic compounds react with polyvinylchloride polymer films containing Jeffamine T-403. Response time and characteristic absorbance for the films will be presented along with a description of the device. The results represent a first step toward a potential solution for detection of vapors utilizing chemically sensitive optical polymers.

Hydrogen based reactive ion etching of zinc sulfide

II–VI materials are important for optoelectronic devices. These devices are currently wet etched and due to the isotropic nature of wet etching, their etch geometries are limited. Reactive ion etching (RIE), a dry etch process, is a more desirable alternative, because it offers a means of producing small anisotropic structures. This study describes the use of a novel hydrogen based RIE chemistry that is shown to clearly etch anisotropic features in ZnS. Etch characteristics as a function of pressure, power, and temperature are presented for both patterned and unpatterned material. Three different types of ZnS films are studied: evaporated, metalorganic chemical vapor deposited (MOCVD), and sputtered. Among the three types of ZnS films investigated, evaporated, and MOCVD consistently etched faster than sputtered ZnS films under the same conditions. However, when patterned, all three ZnS films exhibited similar etch rates.

Amine-containing poly(vinylchloride) membranes for detecting polynitroaromatic vapors above land mines

The goal of our research is to develop a sensitive, rugged, real time sensor for land mine detection. Our method relies upon detecting the change in color arising in an amine- containing poly(vinylchloride) (PVC) film when exposed to polynitroaromatics (the main components of charge in a land mine) in the vapor phase. This change is a result of formation of visible light absorbing complexes between primary or secondary amines and polynitroaromatics. The complex with 2,4,6-trinitrotoluene (TNT) absorbs in the visible domain at 500 nm and the complex with 2,4-dinitrotoluene (DNT), a common contaminant and a degradation product of military TNT, absorbs at 430 nm. Complex accumulates over time so that high sensitivity can be achieved by waiting. The rate of color formation for DNT is ca. 10-5 absorbance units per minute in a saturated DNT vapor atmosphere, at 24 degrees Celsius, when the absorbance is measured through the membrane. Employing the membranes as waveguides would substantially improve sensitivity by increasing the pathlength.

Integrated fault detection capability for Spreeta biosensors

This paper presents integrated fault detection capability of the Spreeta biosensor technology. A specific feature is discussed based on multi-point image characterization. Multi-point image characterization provides a means to monitor biosensor surface damage, as well as sample anomalies such as macroparticulates are bubbles.

Cation impurity interactions in Hg1-xCdxTe

Cation impurity gettering in Hg1-xCdxTe is described in the context of kinetic process models which include the interactions of the impurities and the dominant native point defects. Experimental results are presented using SIMS profiles of Au distributions in Hg0.8Cd0.2Te following Hg anneals and ion mills, which are processes known to inject excess Hg interstitials. In either process, Au is shown to redistribute preferentially to high vacancy regions. The junction depth of the low to high Au transition is determined by SIMS. For Hg rich anneals of Au-doped, high vacancy concentration material, the Au junction behavior with respect to anneal temperature, time, and initial vacancy concentration is shown to follow that expected for type converted electrical junctions in vacancy-only material. For milled Au-doped material with a high vacancy concentration, the Au junction depths are found to be approximately proportional to the amount of material removed. Neither the Hg anneals nor the mills form Au junctions in starting material with a low background vacancy concentration.